Week 2 Discussion Solutions

#Activity

On connection, you should receive the first flag.

socket // Create a socket

connect 3 10.0.1.1 1111 // Connect to system

recv 3 10000 // Receive data from server, second flag here
send 3 NAME HERE // Send name
recv 3 10000 // Receive data from server
send 3 MAJOR HERE // Send major
recv 3 10000 // Receive data from server
send 3 PROF HERE // Send favorite professor
recv 3 10000 // Receive data from server
send 3 TALENT HERE // Send hidden talent
recv 3 10000 // Receive data from server, third flag here

socket // Create a new socket to listen
bind 4 any 2222 // Bind the server socket to port 2222
listen 4 // Start the server
accept 4 // Accept the connection

recv 5 10000 // Read the data sent by the server, fourth flag here

#Platform Questions

#Sockets 1.1

I would like to set up a TCP server, listening on port 8080 for any incoming connections, but not actually make any connections. In what order should I run the following syscalls, if needed? Answer in a comma separated list, like cats,dogs,fish.

• socket,bind,listen - we need to create a socket, bind it to a port, and start the TCP listener

#Socket 1.2

My TCP server is already listening on port 8080. Which of the following syscalls, and in what order, can I use to receive some data from the next incoming connection, and then send some data back? Answer in a comma separated list, like cats,dogs,fish.

• accept,recv,send - we accept the next connection, receive some data, and then send out some data using the TCP syscalls

#Socket 2

I would like to set up a TCP client, connecting to a server on port 8080 at 127.0.0.1, and sending an HTTP GET request and reading the response. In what order should I run the following syscalls, if needed? Answer in a comma separated list, like cats,dogs,fish.

• socket,connect,send,recv - we create a socket, connect outbound to a server, then send and receive data using the TCP syscalls

#Socket 3

I would like to set up a UDP server, listening for any incoming UDP datagrams on port 8080, and reading the data of the first received UDP datagram. In what order should I run the following syscalls, if needed? Answer in a comma separated list, like cats,dogs,fish.

• socket,bind,recvfrom - we create a socket, bind it to a port, and then attempt to read the next UDP packet that arrives on the bound port.

#Protocols 1

Which of the following protocols are used if I logged into gmail.com and sent an email to my friend? Answer as a sorted, comma separated list, like 1,2,3

1. FTP
2. SMTP
3. SIP
4. DASH
5. HTTP
6. STIR/SHAKEN

• 2,5: When sending an email via the gmail.com interface, we use HTTP to visit the site and SMTP to actually send the email.

#Unit Conversion

120 kilobits / second * 1 megabit / 1000 kilobits * 1 gigabit / 1000 megabit * 1 bit / 8 bytes = 0.000015 gigabytes / second * 60 seconds / 1 minute * 60 minutes / 1 hour * 24 hours / 1 day = 1.296 gigabytes / day, 2/3rds of that is 0.864 gigabytes per 2/3rds of a day.